# Making a variable-sized surd?

Is there a get around to make $\surd$ variable-sized via standard AMS package? For example, I would like $\surd \frac{a}{b}$ to look like $\sqrt{\frac{a}{b}}$ with the elongated left line but no overline on $\frac{a}{b}$.

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Welcome to TeX.SX! – Christian Hupfer Aug 7 '14 at 6:15
Hi! It's a nice question. However, from the perspective of math typography, such usage of this symbol is discouraged. It's preferable to always typeset the horizontal bar over the expression you make a root of: $\sqrt{\frac{a}{b}}$. Another solutions for your example are: $\frac{\sqrt{a}}{\sqrt{b}}$ (that's what I prefer) or $\Bigl(\frac{a}{b}\Bigr)^{1/2}$. – yo' Aug 7 '14 at 6:52
@tohecz Thank you for your reply. While I prefer the same style '$\sqrt{\frac{a}{b}}$' that you have suggested, my department is trying to adopt '$\surd$', which seems to be the standard notation for square root employed in Cambridge A-Level examinations. Thus, I am looking for ways to make the symbol '$\surd$' to match '$\sqrt$', minus the overline. – user60342 Aug 7 '14 at 8:19

Use the following definition:

\def\surdex#1{\sqrt{\vphantom{#1}}#1}


and the test:

$$\surdex{\frac{a}{b}}$$

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You probably want to have also the option of setting the root index; with xparse it's rather easy:

\documentclass{article}

\usepackage{xparse}
\NewDocumentCommand{\xroot}{om}{%
\IfNoValueTF{#1}
{\sqrt{\vphantom{#2}}#2}
{\sqrt[#1]{\vphantom{#2}}#2}%
}

\begin{document}

$\xroot{\frac{1}{2}}\ne\xroot[3]{(a+b)}$

\end{document}


Of course, seeing the result I ask myself why a respected institution wants to change a long time honored notation.

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This is the root of ugliness :-/ Especially the LHS. – yo' Aug 7 '14 at 8:54